An electric guitar “harness” is the term of art for the electronic components of an electric guitar, i.e., the circuitry accessed in the rear of the guitar, including electric components like the pickups, switches, potentiometers, and output jacks.
The industry trend in electric guitar and bass guitar designs has been to increase electronic complexity of the harness. These complex circuits require more electronic components, more complicated wiring between electronic components, and overall more complex harnesses that involve multiple wires connecting the individual components.
Using discrete, individual wires in the harness causes numerous problems. In manufacturing multiple hand-soldered joints, or soldering discrete wires, is a potential failure. In effect, three hands are needed to make a reliable solder joint. One hand holds the wire to the component, another hand holds the soldering iron to the wire and the component; and the last hand touches the solder to the heated wire and component. However, a single person solders the wires, using only two hands, and so the quality of the solder joint is a potential failure. The result is often cold-solder joints, i.e., solder joints with cracks in the metal lattice. The cold-solder joint exhibits intermittent electrical failures, or in use, after numerous expansions and contractions, the solder joint fail altogether when the tiny cracks in the joint pull completely apart. Another problem is when discrete wires are connected by hand to one of many terminals. By simple human error wires are accidentally connected to the wrong terminal. Thus, the harness failure rate is increasing as the complexity of the circuitry increases.
Ribbon cables in active guitar systems (i.e., those with battery-powered electronics), and ribbon cable connections in passive components are also novel in the electric guitar and bass industry. The electric guitar industry continues to use the current standard discrete wire and hand-soldered joints described above.